The invention relates to a camshaft for a variable lift valve train of an internal combustion engine. The camshaft comprises a carrier shaft and a cam part that is arranged locked in rotation and movable in the axial direction on this carrier shaft and that is assembled from a cam carrier and a sleeve. The cam carrier has a cam group of directly adjacent cams with different cam strokes and an adapter end on which the sleeve is mounted. The sleeve has a setting groove in the form of a groove that extends at least in some sections across the periphery of the sleeve and that is used for specifying an axial setting groove track for an activation pin moving the cam part on the carrier shaft.
In contrast to switchable cam followers that vary the transmission of cam strokes to gas-exchange valves as a function of their switching state, the valve drive variability in the present camshaft is based on cam parts that can be displaced in the axial direction and whose different cam elevations are in selective engagement with a rigid cam follower. The functional principle of a valve drive with such a camshaft emerges in detail from EP 0 798 451 B1.
A camshaft with a structural configuration according to the class is proposed, for example, in DE 10 2004 022 849 A1, while a construction of the sleeve mounted on the cam carrier for specifying the setting groove track is described in more detail in DE 10 2004 024 219 A1. In these publications, the sleeve mounted on the adapter end of the cam carrier is produced as a separate component made from a steel alloy or a sintered metal. In both cases, however, metal-cutting machining or finishing work is absolutely required on the setting groove formed as a groove, because the spiral-shaped, curved groove walls act as an undercut and, in this respect, the required deformability of a foundry, casting, or sintering mold producing the sleeve as a finished part would not be given. For this reason, the sleeves known in the state of the art can be produced only with high processing and consequently high cost expenditure for the metal-cutting machining or finishing work of the groove.